Doraemon: Nobita's Great Mermaid Naval Battle

Synopsis:

One day, Doraemon and Nobita use the robotic cat's water simulation pump and goggles to fill the town with water and swim alongside countless beautiful fish. After spotting a shark the pair quickly return the fish to where they came from, not realizing that one rare deep-sea creature has been left behind. The following day, Nobita stumbles across a young girl named Sophia in his garden and proceeds to show her around town, but she's no ordinary girl, she's a mermaid princess! When Nobita and the gang proceed to visit her underwater palace, they learn of the lost legendary mermaid sword and decide to search for it; but little do they know that they aren’t the only ones looking for that particular hidden treasure...